Refiner

ABSTRACT

A refining surface for a refiner intended for defibrating lignocellulose-containing materials, the refiner having at least two refining surfaces arranged coaxially relative to each other, at least one of which rotates around a shaft, and between which the material to be defibrated is fed. The refining surfaces define grooves and between them ridges, at least part of the refining surface ridges being formed of at least two different ridge parts connected to each other in such a way that one ridge part is farther ahead in the rotation direction of the refining surface than the other ridge part. Further, at least in some ridge parts, the front wall in the rotation direction of the refining surface is over at least part of its length substantially inclined.

FIELD OF THE INVENTION

The invention relates to a refining surface for a refiner intended fordefibrating lignocellulose-containing material, the refiner comprisingat least two refining surfaces arranged coaxially relative to eachother, at least one of which rotates around a shaft, and between whichthe material to be defibrated is fed, and which refining surfacescomprise grooves and between them ridges, at least part of the refiningsurface ridges being formed of at least two different ridge partsconnected to each other in such a way that one ridge part is fartherahead in the rotation direction of the refining surface than the otherridge part.

BACKGROUND OF THE INVENTION

Disc and cone refiners used for manufacturing mechanical pulp are formedof two refiner discs opposite to each other which turn relative to eachother and one or both of which is/are rotating. In disc refiners therefiner disc is disc-like and in cone refiners it is conical. Therefining surfaces of refiner discs are typically formed of grooves andof protrusions between them, i.e. blade ridges, which will be hereaftercalled ridges. The shape of these grooves and ridges per se may vary indifferent ways. Thus, for example, in the radial direction of therefiner disc the refining surface may be divided into two or morecircular parts, each of which may comprise grooves and ridges ofdifferent shapes. In the same way, the number and density of ridges andgrooves as well as their shape and direction in each circle may deviatefrom each other. Thus, the ridges may be either continuous over thewhole length of the refining surface radius or there may be a pluralityof successive ridges in the radial direction. A plurality of refinersegments consisting of structures formed of ridges and grooves betweenthem are arranged upon the discs. One of the refiner discs comprises anopening through which the material to be refined is fed into therefiner. The refiner discs are positioned in such a way that the refinersegments form a refiner gap, through which the fibre material isintended to be discharged from the inside, where the ridges of therefiner elements carry out the disintegration. The distance between therefiner discs is longest in the middle of the discs, being reducedtowards the outer periphery in order to refine the material gradually.

U.S. Pat. No. 6,311,907 discloses a refiner disc on the refining surfaceof which some of the ridges in the radial direction of the refiner discare formed of ridge parts connected to each other in the radialdirection of the refiner disc in such a way that between the ridge partsof the refiner disc at their connection point, there is a connectingpart that is directed obliquely relative to the direction of the refinerdisc radius, which part connects the ridge parts forming the ridge toeach other in such a way that the ridge travels windingly from thedirection of the inner periphery of the refiner disc to the direction ofits outer periphery. The intention of a winding ridge structure is tomake the refining more efficient by preventing the material to berefined from moving too rapidly out of the space between the refinerdiscs towards the outer periphery of the disc. In one embodiment of thepublication, the connecting part connecting the ridge parts together isdesigned to form an adjacent ramp inclined in the direction of theconnecting part between the ridge parts, the purpose of the ramp beingto facilitate the movement of the material to be refined out of thegrooves between the ridge parts of the refining surface to the spacebetween the refiner discs.

It has also been noted that when fibre material is disintegrated toachieve a better final product, it is advantageous to position flowrestrictors, i.e. what are called dams, across the grooves of therefiner segments so as to prevent untreated material from gettingthrough the refiner gap. The fibre pulp is forced up from the grooves bythe dams and is guided to the treatment between the blade ridges of therefiner segments upon the opposite refiner discs. The more dams thereare in the refiner segment, the higher the quality of the fibre pulpobtained from the refining. In practice, however, the number of damsmust be kept restricted, because the more dams there are in the refinersegment, the more difficult it is for the water in the refiner gap andthe vapour generated due to the high power directed at the disc refinerduring the refining to discharge from the refiner gap, and thus theproduction capacity of the refiner is reduced. In addition, the vapourpressure generates great axial forces between the refiner segments,particularly in the outer part of their periphery, which loads therefiner bearings and thus also restricts the runnability of the refiner.High vapour pressure also causes bending of refiner segments so that thesegments loose their parallelism.

BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is to provide a refining surface of anew type for a refiner intended for defibratinglignocellulose-containing material.

The refining surface according to the invention is characterized in thatat least in some ridge parts in the rotation direction of the refiningsurface, the front wall is over at least part of its lengthsubstantially inclined.

According to an essential idea of the invention, on the refining surfacefor such a refiner intended for defibrating lignocellulose-containingmaterial that has at least two refining surfaces arranged coaxiallyrelative to each other, at least one of which rotates around a shaft andbetween which the material to be defibrated is fed and which refiningsurfaces have grooves and between them ridges and at least part of therefining surface ridges are formed of at least two different ridge partsconnected to each other such that one of the ridge parts is fartherahead in the rotation direction of the refining surface than the otherridge part, the wall on the side of the rotation direction of therefining surface is at least in some ridge parts over at least part ofits length substantially inclined.

Preferred embodiments of the invention are described in the dependentclaims.

An advantage of the invention is that it causes the material to berefined to move more efficiently out of the grooves of the refiningsurface to the space between opposite refining surfaces, providing thushigher quality for the refined final product and keeping the productioncapacity of the refiner high.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be described in greater detail in the attachedfigures, of which

FIG. 1 shows schematically a cross-section of a conventional discrefiner;

FIG. 2 shows schematically a cross-section of a conventional conerefiner;

FIG. 3 shows schematically a typical refiner disc, seen from therefining surface;

FIG. 4 shows schematically a refiner segment according to the invention;

FIGS. 5 a, 5 b, 5 c, 6 and 7 show schematically ridges and groovesaccording to the invention, located on the refining surface; and

FIGS. 8, 9 and 10 show schematically ridges on the refining surfaceaccording to the invention.

For the sake of clarity, the invention is shown simplified in thefigures. Similar parts are denoted with the same reference numerals.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows schematically a side view and cross-section of aconventional disc refiner. The disc refiner comprises two disc-likerefining surfaces 1 and 2, which are positioned coaxially relative toeach other. In this embodiment, one refining surface 1 is in a rotatingrefiner disc 3, which is rotated by means of a shaft 4. The otherrefining surface 2 is in this case in a fixed refiner disc 5, i.e. in astator. The refining surfaces 1 and 2 in the refiner discs 3 and 5 maybe either formed directly to the discs or formed of separate refinersegments in a manner known per se. Further, FIG. 1 shows a loader 6connected to affect the refiner disc 3 via the shaft 4 in such a waythat it can be pushed towards the refiner disc 5 to adjust the openingbetween them. The refiner disc 3 is rotated via the shaft 4 in a mannerknown per se by means of a motor not shown for the sake of clarity.

The lignocellulose-containing material to be defibrated is fed throughan opening 7 in the middle of the other refining surface 2 to theopening between the refining surfaces 1 and 2, i.e. the refiner gap,where it is defibrated and ground at the same time as the water in thematerial vaporizes. The lignocellulose-containing material to bedefibrated can be fed into the refiner gap also through openings on therefining surface 2, which are not shown in the figure for the sake ofclarity. The lignocellulose-containing material that has been defibratedis discharged from the space between the refiner discs through anopening between the discs, i.e. from the outer edge of the refiner gap,into the inside of a refiner chamber 8, from where it is furtherdischarged along a discharge channel 9.

FIG. 2 shows schematically a side view and cross-section of aconventional cone refiner. The cone refiner comprises two conicalrefining surfaces 1 and 2, which are positioned within each othercoaxially. In this embodiment, one refining surface 1 is in a rotatingconical refiner disc 3, which is rotated by means of the shaft 4. Theother refining surface 2 is in this case in a fixed conical refiner disc5, i.e. in a stator. The refining surfaces 1 and 2 of the refiner discs3 and 5 may be either formed directly to the discs or formed of separaterefiner segments in a manner known per se. Further, FIG. 2 shows aloader 6 connected to affect the refiner disc 3 via the shaft 4 in sucha way that it can be pushed towards the refiner disc 5 to adjust theopening between them. The refiner disc 3 is rotated via the shaft 4 in amanner known per se by means of a motor not shown for the sake ofclarity.

The lignocellulose-containing material to be defibrated is fed throughan opening 7 in the middle of the refining surface 2 into a conical gapbetween the refining surfaces 1 and 2, i.e. conical refiner gap, whereit is defibrated and ground. The lignocellulose-containing material thathas been defibrated is discharged from the space between the refinerdiscs through an opening between the discs, i.e. from the outer edge ofthe refiner gap, into the inside of the refiner chamber 8, from where itis further discharged along the discharge channel 9.

FIG. 3 shows schematically a typical refining surface of a disc refiner,seen from the axial direction. The refining surface comprises in theperipheral direction of the refiner alternately grooves 10 and ridges 11at the same point. The refining surface also comprises flow restrictors,i.e. what are called dams 18, arranged across the grooves 10, with whichuntreated material is prevented from getting out of the refiner gap. Thedams 18 force the fibre pulp out of the grooves 10 but make it moredifficult for the water and the vapour generated due to the high powerdirected at the refiner during the refining to discharge from therefiner gap. By way of example, the refining surface has been heredivided in the radial direction into two successive circles with groovesand ridges of different shapes compared with each other. Hence, by wayof example, the ridges in the outer circle may be curved over at leastpart of their length, as shown in FIG. 3, relative to the rotationdirection indicated by arrow A, in such a way that the intermediatematerial on the outer periphery of the refining surface is “pumped” fromthe refiner outwards. There are, in a manner known per se, severaldifferent refining surfaces formed either directly to the refiner discor of different surface elements.

FIG. 4 shows schematically a part, i.e. segment, of the refining surface1 according to one solution, where the refining surface 1 is, by way ofexample, divided into two circles 12 and 13 that are successive in theradial direction. The ridges 11 of the inner circle 12 are shaped insuch a way that they are formed of at least two different ridge parts 11a and 11 b. The ridge parts 11 a and 11 b are connected to each other insuch a way that the ridge part 11 a closer to the central shaft 4, i.e.the rotation shaft of the refining surface 1, is at the connecting pointof the ridge parts 11 a and 11 b farther behind relative to the centralshaft 4 in the rotation direction indicated by arrow A than the ridgepart 11 b farther off from the central shaft 4. The ridge parts 11 a and11 b may also be connected to each other in such a way that the ridgepart 11 a closer to the central shaft is at the connecting point of theridge parts 11 a and 11 b farther ahead relative to the central shaft 4in the rotation direction than the ridge part 11 b farther off from thecentral shaft 4. The ridge parts 11 a and 11 b may also have thedirection of the radius of the refining surface 1, or they may curveforwards relative to the rotation direction of the refining surface. Theouter circle 13 is shaped in such a way that the grooves 10 and ridges11 in it are radial, or they may be directly or curvingly −45 to +45degrees in relation to the radius of the refining surface 1. Thesegments of the refining surface 1, i.e. the refiner segments, may alsobe formed of only one circle similar to the inner circle 12. They mayalso be formed of several circles similar to the inner circle 12 andouter circle 13. The flow of vapour generated due to the high powerdirected at the refiner during the refining and the flow of waterpresent in the refiner gap in the grooves 10 need not necessarily beprevented with dams.

FIGS. 5 a, 5 b and 5 c show schematically some potential embodiments ofthe ridges 11 on the refining surface according to the solution. FIG. 5a shows ridges 11 seen from the direction perpendicular to the refiningsurface 1, FIG. 5 b shows a cross-section of the ridge part 11 a at thesection point D, and FIG. 5 c shows a cross-section of the ridge part 11a at the section point E. The lingocellulose-containing material isguided for refining into the refiner gap with the aid of the centrifugalforce caused by the rotation of the refiner discs and surfaces via thewall 14 of the side profile of the ridge part 11 a farther ahead in therotation direction of the refining surface 1 and an oblique bevel 15between the ridge parts at the connecting point of the ridge parts 11 aand 11 b. The vapour generated due to the high power directed at therefiner during the refining and the water are discharged out of therefiner along the bottom of a groove 17, because they have a lowerdensity than the lignocellulose-containing material, and thus thecentrifugal force affecting them is lower than the centrifugal forceaffecting the lignocellulose-containing material. Therefore, they areguided in the direction where there is open space for flows directedaway from the central shaft 4, i.e. the rotation shaft of the refiningsurface. Designing and dimensioning the shape of the walls 14 and bevels15 of the ridges as well as their position in the longitudinal directionof the ridges 11, i.e. in the radial direction of the refining surface1, provides a situation where the lignocellulose-containing material isguided to a refining zone between the refining surfaces 1 and 2, and thevapour and water are discharged out of the refiner along the bottom ofthe groove 17.

The wall 14 of the ridge parts 11 a and 11 b is shaped oblique orinclined backwards relative to the rotation direction A of the refiningsurface 1 in such a way that angles α1 and α2, shown in FIGS. 5 b and 5c, are formed between the plane normal of the refining surface 1 and theinclined wall 14. Angle α1 indicates the inclination of the ridge partcloser to the rotation shaft of the refining surface 1, and angle α2indicates the inclination of the ridge part farther off from therotation shaft of the refining surface 1. The inclination of the wallmay remain the same over the whole longitudinal direction of the ridgepart 11 a and 11 b, whereby the angles α1 and α2 are equal over thewhole length of the ridge part, but preferably the inclination of thewall of the ridge part increases when moving forwards along the ridgeparts 11 a and 1 b towards the outer periphery of the refining surface1; in other words, α2 is thus greater than α1. The magnitude of angle α2closer to the outer periphery of the refining surface 1 may vary between15 to 60 degrees, preferably between 30 to 50 degrees, whereas themagnitude of angle α1 closer to the rotation shaft of the refiningsurface 1 may vary between, for instance, 0.5 to 5 degrees, butpreferably angle α1 is at least 10 degrees smaller than angle α2. Themagnitude of the angle has the effect that the greater the angle, themore efficiently the material to be refined is guided between therefining surfaces. Thus, when the wall of the ridge part of the refiningsurface having a great angle of inclination encounters the correspondingwall of the ridge part of the opposite refining surface, the pressurepulse generated between the walls is low, which facilitates the liftingof fibres to the refining, making thus the refining more efficient andimproving the pulp quality. Since the inclination of the ridge part wallof the refining surface increases when moving in the direction of theouter edge of the refining surface, the refining effect directed at thematerial to be refined can be made more efficient when the material tobe refined moves between the refining surfaces from the centre of therefining surface in the direction of the outer edge before the materialto be refined moves out of the space between the refining surfaces. Thefarther on in the direction of the outer periphery one moves, the morethe refining area increases, and therefore also, it is particularlyadvantageous for the material to be refined to be guided moreefficiently than before out of the grooves to the space between therefining surfaces when moving in the direction of the outer periphery.

The figures show that the wall of the ridge part 11 a and 11 b in therotation direction A of the refining surface 1 is oblique or inclinedover the whole length of the ridge part, but it may also be the casethat the wall is oblique or inclined only over part of the ridge partlength.

When the wall 14 of the ridge parts 11 a and 11 b in the rotationdirection A of the refining surface 1 is made oblique or inclined overat least part of the length of the ridge part 11 a and 11 b, thematerial to be refined moves more efficiently out of the grooves 17between the ridges 11 to the upper surface of the ridges 11 betweenopposite refining surfaces. Thus, the quality of the refined finalproduct can be improved and the production capacity of the refiner canbe kept high. Further, the movement of the material to be refined to thespace between the refining surfaces 1 and 2 may be made more efficientwith an oblique bevel 15 formed at the connecting point of the ridgeparts 11 a and 11 b, which bevel is designed to rise from the directionof the ridge part 11 a closer to the rotation shaft of the refiningsurface 1 towards the ridge part 11 b farther off from the rotationshaft of the refining surface 1, and which bevel 15 preferably extendsas far as to the upper surface of the ridge part 11 b. These obliquebevels 15 can be formed at all connecting points of the ridge parts 11 aand 11 b of the refining surface 1, or at only some of them.

FIG. 6 shows schematically an oblique top view of the ridges 11 on therefining surface 1, seen from the direction opposite to the rotationdirection A of the refining surface 1. Further, FIG. 6 indicates witharrow B the flow of vapour and water in the groove 17 between the ridges11, and with arrow C the movement of the lignocellulose-containingmaterial to the refining zone between the refining surfaces 1 and 2 bymeans of an oblique bevel 15 at the connecting point of the ridge parts11 a and 11 b. FIG. 6, in the same way as FIG. 5, also shows betweenadjacent ridge parts in the rotation direction of the refining surface 1dam-like structures 18 and 19 connecting the ridge parts together, whichstructures guarantee that the lignocellulose-containing material risesfrom the groove 17 into the refiner gap between the refining surfaces tobe treated. The structures 18 and 19 may extend to the upper edge of theridge part or to only part of its height.

FIG. 5 a shows that the front wall of the ridge 11 in the rotationdirection A of the refining surface 1 in the plane of the groove 17 ofthe refining surface 1 is continuous, in other words the wall of theridge part 11 b continues uninterruptedly with the wall of the ridgepart 11 a without staggering in the plane of the refining surface 1 whenone moves in the radial direction of the refining surface 1 from thedirection of the inner periphery of the refining surface 1 towards theouter periphery of the refining surface 1. FIG. 7 further shows anembodiment of the ridge 11 where said wall of the ridge 11 on theright-hand side of the figure is not continuous in the plane of thegroove 17 of the refining surface 1, but there is in the rotationdirection of the refining surface 1, 2 between the front edges of thewalls of the ridge parts 11 a and 11 b small staggering or a small step20 in the plane of the groove 17 at the connecting point of the ridgeparts 11 a and 11 b. The step may even be so big that it begins at thesection of the side of the outlet edge of the ridge part located fartheron and the bottom plane of the ridge part, in which case the step formsat the same time a dam. Depending on the angle of the step point,however, the dam does not necessarily prevent the flow in the grooveessentially, but it guides material to be refined effectively to thespace between the refining surfaces. FIGS. 8, 9 and 10 further showschematically and by way of example some feasible shapes of the ridges11 of the refining surface 1 according to the solution. The ridges 11 ofFIGS. 8, 9 and 10 are characterized in that the lower or front edge ofthe ridge parts follows a continuous line, in other words the ridgeparts of the ridge 11 extending from the bottom of the refining surfacefollow a continuous line, which may turn in several different ways. Ifthere is a step at the connecting point of the different ridge parts ofthe ridge 11, there must also be at the point of the step a greaterangle between the normal of the refining surface and the inclined wallof the ridge part than at the start of the next ridge part.

The drawings and the related description are only intended to illustratethe idea of the invention. The details of the invention may vary withinthe scope of the claims. Thus, the structural solutions of the segmentsof the refining discs may vary per se, whereby either one or both of therefining surfaces may be surfaces according to the invention. Therefining surfaces are typically vertical and rotate around a centralshaft, but it is also feasible to apply the invention to solutions wherethe refining surfaces are horizontal. The refining surfaces may also becylindrical or conical. Further, the invention may be applied tolow-consistency refining and refining of fibreboard fibres. The refiningsurface according to the solution may naturally be used also in suchrefiners where between two refiner discs arranged fixedly, i.e. twostators, there is one rotating refiner disc, on both sides of whichthere is a refining surface, or in refiners where both refining discsare rotating. In the examples of the figures, the rotation direction Aof the refining surface is indicated to be from left to right, but itmay naturally be from right to left as well, in which case the shape ofthe ridges 1 naturally changes in such a way that the inclined wall 14of the ridges 11 is towards the rotation direction, i.e. at the leftedge of the ridges 11 as compared with the figures.

1. A refining surface for a refiner intended for defibrating lignocellulose-containing material, the refiner comprising at least two refining surfaces arranged coaxially relative to each other, at least one of which rotates around a central shaft in a rotation direction, and between which the material to be defibrated is fed, and wherein at least one of the refining surfaces comprises grooves and between them ridges, at least part of the refining surface ridges being formed of at least two different ridge parts each defining a length connected to each other in such a way that one ridge part is farther ahead in the rotation direction of the refining surface than the other ridge part and that at least some ridge parts define a wall relative to the rotation direction of the refining surface which defines an inclination relative to the shaft over at least part of its length, wherein the inclination of the wall of the ridge part changes along at least part of the length of the ridge part in such a way that the inclination of the wall closer to the central shaft of the refining surface is smaller than the inclination of the wall farther off from the central shaft of the refining surface.
 2. A refining surface according to claim 1, wherein the inclination of the wall of the ridge part is between 0.5 and 60 degrees.
 3. A refining surface according to claim 1, wherein the ridge part closer to the central shaft of the refining surface is, at the a connecting point of the ridge parts in the rotation direction of the refining surface farther behind than the ridge part farther off from the central shaft.
 4. A refining surface according to claim 1, wherein the ridge part farther off from the central shaft of the refining surface is, at the connecting point of the ridge parts, in the rotation direction of the refining surface farther behind than the ridge part closer to the central shaft.
 5. A refining surface according to claim 1, wherein the two successive ridge parts define front edges that are continuous when seen from the rotation direction of the refining surface.
 6. A refining surface according to claim 1, wherein the two successive ridge parts define front edges that are staggered relative to each other when seen from the rotation direction of the refining surface.
 7. A refining surface according to claim 1, wherein at least some of the ridge parts are connected to each other, and define an oblique bevel inclined towards the outer edge of the refining surface.
 8. A refining surface according to claim 1, wherein the ridge parts define upper surfaces that are in the same plane.
 9. A refining surface according to claim 1, further comprising at least one dam structure between ridge parts adjacent in the rotation direction of the refining surface, connecting said ridge parts together. 